The present invention relates generally to methods and apparatus for generating a perspective corrected view of a portion of a wide angle image acquired, for example, by utilizing a fish-eye lens. More particularly, the invention provides methods and apparatus for linking the wide angle image and a perspective-corrected view of a portion of that image.
Imaging systems that utilize fish-eye lenses are known in the art. A fish-eye lens captures an image corresponding to a hemispherical, or a partially hemispherical, field of view. That is, fish-eye lenses allow imaging much-enhanced angular views relative to views obtainable by ordinary camera lenses. An image obtained by a fish-eye lens, however, contains radial distortions that need to be rectified to allow convenient viewing.
Methods and devices for selecting and undistorting a portion of a fish-eye image are also known. Such conventional methods and devices, however, suffer from a number of limitations. For example, although such conventional devices present an undistorted view of a portion of a fish-eye image, they do not allow a viewer to observe simultaneously the relation of the undistorted view to the entire image using a single imaging device. In other words, such conventional devices do not allow a viewer to observe simultaneously an undistorted view of a portion of a fish-eye image, and the remainder of that image, albeit with distortions introduced by the fish-eye lens present.
Moreover, conventional methods for undistorting a portion of a fish-eye image have a number of shortcomings. Such conventional methods can only be utilized for removing distortions from image portions corresponding to a small field of view. For example, these methods break down completely when applied to image portions corresponding to fields of view of tens of degrees, resulting in smeared images. Such limited viewing angles provided by conventional methods diminish considerably the benefits of panoramic observation of a scene.
Accordingly, there is a need for methods and apparatus for acquiring and viewing a fish-eye image that provide canonical undistortion capability, and afford enhanced flexibility for viewing portions of the fish-eye image throughout the full 180-degree field of view while compensating for distortions introduced by the fish-eye lens.
Further, there is a need for methods and apparatus which allow readily selecting a portion of a fish-eye image, generating a perspective-corrected view of the selected portion at a desired magnification without losing the benefits of panoramic aspects of viewing a scene provided by the fish-eye lens.